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Survey of Super Massive Black Holes Completed
eldavojohn writes "NASA has announced the completion of a survey of nearby supermassive black holes. Every galaxy that revolves around a supermassive black hole within 400 light-years of our own galaxy has been cataloged. From the article: 'Called active galactic nuclei, or AGN, these black holes have masses of up to billions of Suns compressed into a region about the size of our solar system. The all-sky census, performed using NASA's Swift satellite over a nine-month period, detected more than 200 nearby AGN.' I'm starting to feel very lucky to have grown up in the Milky Way Galaxy."
400 lightyears? Didn't the submitter read the article?
It's 400 *million* light years.
I'm starting to feel very lucky to have grown up in the Milky Way Galaxy.
Yes. Living near one of those super-massive black holes would certainly suck. Being one with everything around you sounds nice and radiant - but it leaves you all strung out over time, and it seems to take forever! The light at the end of the tunnel is you.
Ryan Fenton
That would be 400 million light years. 400 light years wouldn't get you out of our local arm of the Milky Way.
Hate to break it to you, but there's a >million solar mass black hole at the center of our galaxy. We're not considered an "Active Galaxy" only because it is on a diet.
Almost every major galaxy including the Milky Way has been found to have a supermassive black hole at its core. The only lucky part is our sun not being near to the core of the galaxy, not which galaxy it is in.
Donte Alistair Anderson Roberts - hi son!
Karma: Chameleon
Considering our space boffins have a problem seeing large asteroids really close up -- not even one light second away -- http://www.cnn.com/2002/TECH/space/06/20/asteroid. miss/ why should we believe that they have seen all the black holes many light years away?
Engineering is the art of compromise.
100 black holes surveyed, top 5 answers on the board...
Absolutely ridiculous. >.>
They are black and holey
Oh great, did you have to bring race *and* religion into this?
Table-ized A.I.
The article says that it is every super massive black hole within 400 million light years. Also, as for being "lucky" to be in the Milky Way, our Galaxy has a super massive black hole at the center of it. Actually, we are a very typical galaxy. We are slightly larger than the average and we are a spiral galaxy (there are more elliptical galaxies and irregular galaxies than spiral). We are very typical. Also, as for being lucky about not being closer to the center of the galaxy (someone above mentioned that as well) if we were closer to the black hole at the center, it would not mean much. We are in an orbit around it and thus we won't be falling into it any time soon, even if we were closer to it. We do, though, have a great location in the galaxy. We are far enough out that we can look across the plane of our galaxy (only at some wavelengths because dust obscures a lot) and get a good view of it. We also can look out pretty well too. And to make things even cooler, our solar system actually bobs up and down through the main plane of the galaxy. It take about 30 million years to complete a complete cycle, but in 5 or so million years we will have a pretty cool view from above of the Milky Way. I don't remember exactly what the angle is that we would be viewing the galaxy from, not huge, but enough to be useful. The point of all this is that the advantage of this survey is to have a complete list of super massive black holes so as we are testing out theories we can apply these theories (and how they measure up) across not only a wide data set, but also a very complete set. There is so much left to be learned about black holes and this catalogue will certainly help.
The average density of a supermassive black hole can be very low, and may actually be lower than the density of water.
That sounds suspicious, especially coming from wikipedia. Something with a density that low could not likely bend light enough to keep it from escaping, even if very large.
Table-ized A.I.
The average density of a supermassive black hole can be very low, and may actually be lower than the density of water.
That sounds suspicious, especially coming from wikipedia. Something with a density that low could not likely bend light enough to keep it from escaping, even if very large.
The singularity that bends light does not have that low density. It has an incredibly high density. But the AVERAGE density is the mass of the singularity divided by all that space inside the event horizon.
First, the diameter of a "black hole" is proportional to its mass. The sun, for example, must be compressed to a diameter of about 3km to become a black hole. A black hole with the mass of billion suns would have a dameter=3 billion km or 1000 times our solar system. The density of this black hole would be "low" as in much thinner than air. (Do the math yourself. Mass of sun is 2x10E30kg)
Anyway, as a region of space gets denser, time slows down, and as the density approaches the density required to become black hole, time just freezes.
What you will see when looking at a "black hole" is just a region of space with the eventual event horizon of the hole just frozen in time, and as you move outside, time goes through the "molasses" stage, and as you get further away, gets normal.
The black hole will not form in any finite time since time there just stopped!
For the observer falling towards the "hole", time in the rest of the universe just speeds up. In a matter of minutes the universe will age billions of years, and the observer will first hand know the ultimate fate of the universe in a distant future.
don't cut it off www.mgmbill.org
I wonder if the editors purposefully put factual errors in there just to sit back and watch the orgie of "OMG NO THATS WRONG" comments that invariably follow. 400 light years? Of course it's a mistake. Is there anyone who reads /. that doesn't know that 400 light years is a little close for a galaxy? Of course, there are those that get positively horny over the propsect of correcting factual errors.
Because hey, trivia = intelligence, right?
Every galaxy that revolves around a supermassive black hole within 400 light-years of our own galaxy has been cataloged.
The whole catalog:
1. Our own galaxy
It would sound more reasonable coming from Slashdot? What source of information on the Web do you think is more reliable? I've certainly fixed my share of errors on Wikipedia, but that's becuase I hunt them down, as do many others. That kind of fact-checking is almost non-existant on most of the Web, so if I'm going to trust any one source (and I don't) for such information, it would be Wikipedia.
And, as others have noted, you were mis-understanding the definition of "average density". There's a fairly well-known calculation that states that a spherical volume of material with the density of water, and a diameter less than that of Jupiter's orbit would form an event horizon, effectively constituting a black hole. It's a nice visualization of a complex phenomenon. R. Huber has done the math for us (pdf) if you want to check for yourself.
Suspicious? Let's see. "The solar system"/supermassive black hole is about 16 light-hours across.
57600 light-seconds
10713600000 miles
The sun is 800,000 miles across. So, width-wise, the solar system is
13392 suns wide
Volume is the cube of the linear width, so the solar system could fit
2,401,797,132,288 sunc
in its volume.
Although the density of the core of the sun is very high, I'm thinking it's not so high that "billions" of suns would make such a volume be denser than water when that volume could hold two and a half trillion suns just to be as dense as one sun.
It may be more on the order of as dense as a helium baloon, or even lighter.
(-1: Post disagrees with my already-settled worldview) is not a valid mod option.
It's nice to see a skeptic; It's a virtue to be a skeptic and not a sin. However, in this case your skepticism is misplaced.
The simplest black hole solution to the equations that govern General Relativity is Schwarzschild's solution. In this he shows that the radius of a black hole is directly proportional to its mass. Elementary geometry tells us that the volume of a sphere is proportional to the cube of the radius. Therefore, the density, which is just mass over volume, that is required to create a blackhole decreases the more mass you have.
I find the figure fairly reasonable for the amount of mass these super-massive black-holes contain.
Simon
The narrator on the video keeps going on about look 78 billion light years into the universe but that is wrong. The universe only formed 13.7 billion years ago so the furthest we can see is 13.7 billion light years due to relativity. Inflation may mean the Universe is bigger bit we will not be able to see it if it is.
In actual fact the WMAP probe is the furthest we have seen, NOT the Hubble deep field since that looks at the Universe ~300k years after the Big Bang before there were any stars, let alone galaxies.
That said it was a nice video but it would have been nicer if they got their facts correct when trying to sound impressive!